The Briton won the first set of her match against home hope Mandy Minella but was pegged back in the second, losing it 6-1.
However, Keothavong held her nerve, wrapping up the third set 6-3 for a success which lasted just short of one hour 49 minutes.
Fellow Briton Elena Baltacha's interest in the tournament ended in the first round at the hands of Julia Goerges.
The 28-year-old bowed out 7-5 6-1 to the German in an hour and 20 minutes.
Elsewhere, Romania's Alexandra Cadantu defeated Anastasiya Yakimova, of Belarus, 6-1 6-4.
Italy's Alberta Brianti saw off Georgia's Anna Tatishvili 6-3 1-6 6-3 and Canada's Rebecca Marino ousted Russia's Anastasia Pavlyuchenkova 1-6 6-3 6-3.
Romania's Monica Niculescu defeated Italy's Karin Knapp 6-7 (2/7) 7-5 7-6 (7/3) and the Czech Republic's Lucie Hradecka knocked out Slovakia's Daniela Hantuchova 6-7 (3/7) 7-5 6-1 in Tuesday's other games.